The present invention relates to a process for the manufacture of a series of photoconductor webs, by coating an electrically conductive surface disposed on a carrier web with a solution containing a photoconductive substance and drying the web. Coating is effected in the form of coated sections separated from each other by spacing strips extending transversely to the axis of the carrier web. Further, the invention relates to an apparatus for performing a preferred embodiment of the inventive process.
Web-shaped carriers coated with photoconductor layers are used in electrophotographic copying apparatuses. Electrically conductive papers, films, fabrics and metal foils may be used as carrier webs, metal-coated plastic films being preferred because of their high dimensional stability and good flexibility. During their use in a copying apparatus, the photoconductive layers are subject to a higher or lower degree of wear, because for each copy toner must be scattered onto the photoconductive surface. For this reason, a relatively large number of photoconductor layers of the required length are stored in the copying apparatus in the form of a photoconductor web rolled up in a film magazine in the manner of a photographic film. In order to provide a definite zero potential, which is required for the charge to leak off during exposure of the charged photoconductor layer, a contact surface of adequate size must be provided for grounding the conductive carrier. Two alternatives exist to provide a metallic contact with the grounding, viz. to leave a strip extending along one or both edges of the photoconductive web uncoated with photoconductor, or to provide one, or preferably both, ends of the photoconductively coated sections with contact strips extending transversely to the longitudinal axis of the photoconductor web.
Particularly in the case of metallized plastic films the production of the contact surfaces offers problems. Metal strips extending along the web and left uncoated have the disadvantage that sliding contacts must be provided to enable the charge to leak off, and that such sliding contacts are sensitive and prone to trouble and do not allow for a quick, reliable discharge because the contact surfaces are relatively small. Therefore, photoconductor webs are preferred which have adequately sized contact areas extending over their entire widths at both ends of each photoconductively coated section. So far, no process has become known by which photoconductor webs having such contact areas may be manufactured in series, i.e., in the form of a large number of webs connected with each other to form a coherent row from which individual photoconductor webs may be obtained by severing between the coated sections.
U.S. Pat. No. 2,933,061 describes an apparatus by means of which a smooth, uniform layer may be applied to a web of paper or similar material conveyed at a uniform speed in its longitudinal direction. This known device is equipped, inter alia, with a slot die and a rotary backing roller. The slot die serves to apply a coating solution, and the backing roller serves as a support for the web while the coating solution is applied. The backing roller is mounted so that it rotates about its horizontal axis and the slot die is arranged in such a manner that its orifice is parallel to the axis of the backing roller and may be moved close to the surface of the backing roller and removed therefrom. The slot die is equipped with a die chamber in which the coating liquid to be applied is stored. The die chamber may be connected with a device my means of which its contents of coating solution are constantly replenished. When the slot die is moved into the position where it is close to the backing roller, the die orifice is open, whereas it is closed by a lamella or a similar closing device when the slot die is away from the backing roller. This apparatus may thus be used for applying to a web of material coated sections interrupted by the desired spacings. The apparatus is practically unsuitable, however, for the manufacture of a series of photoconductor webs, because it does not allow the application of layers, the thickness of which can be adjusted with an adequate degree of accuracy. Above all, it is almost impossible, when using this known coating device, to prevent the layer from turning out slightly thicker at the beginning of the coated sections. Such thicker areas are of particular disadvantage because they produce permanent marks in the metallic surface of the coated webs when these are wound into rolls, and the marks are then reflected as defects in the copies produced by means of this photoconductor layer.